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[FAQ] TI Ethernet PHY Capacitive Coupling (Transformerless Operation)

Other Parts Discussed in Thread: DP83869, DP83825


All of our Industrial Ethernet PHYs support Transformer-less Operation via Capacitive Coupling except for the DP83867.

The DP83867 does not support Transformer-less Operation.

List of Industrial Ethernet PHYs that support Transformer-less Operation:

  • DP83869 
  • DP83848
  • DP83822
  • DP83826
  • DP83825


Our Physical Layer Ethernet PHYs typically have the same functional topology.

Figure 1 - DP83869 Typical Copper Application

The Block labeled "Magnetics" is what this FAQ will be discussing. 

A typical application will use a Transformer, mainly to keep the network cable DC isolated (the Cable connector from Figure 1).

Figure 2 - Typical 10/100 Mbps Twisted Pair Interface

However a transformer is not the only solution to isolate DC Voltage. Isolation that transformers provide can be realized using non-polarized capacitors.

Figure 3 - Transformer-less Configuration

Further Details can be found in the following Application Note: 

DP83848 Transformer-less Operation



Alvaro Reyes